How can i make an interesting tree trunk without having to sculpt it?
As I know from my expierience with substance designer you can create almost everything with a height-map and a Displacement Modifier. Since blender has the amazing possibility to create stunning procedural textures, I would go with that. Create a few basic trees, with some branches and apply a procedural displacement-map on it, you can create it in the node-editor. The big advantage of procedural textures in blender is to create many different variations by just tweaking a few parameters, in blender you can even use the position of your trees as a driver for different parameters, it's not the easiest thing to do, but it creates a lot of realistic varaitions once you've done the node setup. If you have no expierience with procedural textures, you can watch a few youtube tutorials how tree-barks are made procedural. This is what I found.

https://youtu.be/Rh5gAQLtOls
https://youtu.be/tS3D3cSgRyE
https://www.blendernation.com/2019/03/14/download-procedural-pine-bark-shader/
https://docs.blender.org/manual/en/2.79/render/blender_render/textures/types/procedural/index.html

All the best Marco